A portable environment for developing parallel FORTRAN programs

The emergence of commercially produced parallel computers has greatly increased the problem of producing transportable mathematical software. Exploiting these new parallel capabilities has led to extensions of existing languages such as FORTRAN and to proposals for the development of entirely new parallel languages. We present an attempt at a short term solution to the transportability problem. The motivation for developing the package has been to extend capabilities beyond loop based parallelism and to provide a convenient machine independent user interface. A package called SCHEDULE is described which provides a standard user interface to several shared memory parallel machines. A user writes standard FORTRAN code and calls SCHEDULE routines which express and enforce the large grain data dependencies of his parallel algorithm. Machine dependencies are internal to SCHEDULE and change from one machine to another but the users code remains essentially the same across all such machines. The semantics and usage of SCHEDULE are described and several examples of parallel algorithms which have been implemented using SCHEDULE are presented.